tolerate internet latency for initial inputs

packages/engine/test/engine.test.mjs

@@ -151,6 +151,34 @@ test("the developer-facing API compiles named sections into a networked game", (
   );
   server.step();
   assert.equal(server.currentState.value, 3);
+
+  // Internet clients can be several ticks behind the server when their first
+  // input arrives. Accept it within the default one-second transport window
+  // and apply it on the next authoritative step.
+  for (let index = 0; index < 6; index++) server.step();
+  assert.deepEqual(
+    server.submitInput(1, {
+      sequence: 2,
+      targetTick: 2,
+      observedTick: 2,
+      input: { amount: 2 },
+    }),
+    { accepted: true },
+  );
+  server.step();
+  assert.equal(server.currentState.value, 5);
+
+  for (let index = 0; index < 7; index++) server.step();
+  assert.deepEqual(
+    server.submitInput(1, {
+      sequence: 3,
+      targetTick: 2,
+      observedTick: 2,
+      input: { amount: 2 },
+    }),
+    { accepted: false, reason: "past" },
+  );
+
   assert.deepEqual(codec.decode(codec.encode({ unicode: "flux ⚡" })), {
     unicode: "flux ⚡",
   });